The present invention generally relates to apparatus and methods for cutting tube and duct assemblies to a planar scribe line and, more specifically, to apparatus and methods for cutting curved tube and duct assemblies using a high powered laser and a vision system which locates and measures a scribe line in a plane on the duct, thus determining its orientation.
Modern aircraft, automobiles, ships, power plants, and the like, utilize round nickel-based metal alloy, stainless steel, aluminum, titanium and other similar materials for ducts and tubes used for many applications, including the transfer of gases and fluids from one location to another. For example, welded duct assemblies and tubes are used for various systems on commercial aircraft, including engine bleed air ducting, thermal anti-ice ducting, engine starter ducting, auxiliary power unit ducting, and air conditioning ducting. In fact, for large complex commercial aircraft, there are several hundred detailed ducting parts that are welded together to form particular duct assemblies. The detailed ducting parts have varying diameters, curvatures, and lengths, and are formed by a Computer-Aided Numerical Control (CNC) tube bender to nearly every conceivable three-dimensional configuration.
The current practice at most parts fabrication shops, is to place the formed ducts and tubes into a fixture, such as a weld fixture, and to manually scribe a trim line around the part. FIG. 1 illustrates a typical duct trim diagram, where a scribe line 12 is placed along the outer circumference of typical curved duct 10 at the location where the final cut is to be made. The scribe line 12 is always in a plane 18 and is generally within an angle 16, which is perpendicular, within approximately 5 degrees, to the duct centerline 14. Because manufacturing processes are not normally precise due to duct and tube bending tolerances, weld fixture inaccuracies, and part placement repeatability, there are variations from one duct or tube assembly to the other, and thus each duct and tube detail must be individually scribed and cut.
Current cutting and trimming methods include band saws, friction saws, hand-held plasma arc, rotary shears and nibblers. Shop mechanics trim the tube or duct close to the scribe line using such well-known devices and then grind the remaining material up to the scribe line. All these operations are manual and each cut edge requires grinding and other hand finishing for a proper fit, thus resulting in a very labor-intensive operation. In addition, there are significant safety concerns with these manual methods because the mechanics hands are quite close to the blades and shears. Also, welded ducts with thicker walls, specially nickel-based metal alloy, are very difficult to trim with these manual methods.
Prior attempts to resolve this problem have included the introduction of more powerful saws, rotary shears, and hand held plasma-arc cutting systems. Though these trim a little faster, they still represent manual methods that require hand finishing, and also continue to pose a significant safety hazard. A duct trim tool using a conventional metal cutter has been employed advantageously in the past. However, such a tool is limited in that it is only capable of trimming straight tubes and ducts, and it is not a fast operation. Additionally, the most important limitation of this type of tool is that, particularly for aircraft, the vast majority of tubes and ducts (over 80%) are of a curved configuration.
A 5-axis numerically controlled laser machine is also not practical for cutting the ends of ducts, or for curved ducts. It would be very time consuming to find and record (xe2x80x9cteachxe2x80x9d) the machine to cut a scribe line, as such a machine requires the generation of unique CNC part-programs (motion databases) for each single operation. Also such a machine would require a tooling system to hold and position the hundreds of different configuration curved ducts and tubes to be cut.
U.S. Pat. No. 5,744,778 to Kash, et al. discloses a laser cutting machine that has a tube stock support bearing assembly on the cutting head itself. The support bearing assembly includes an indexing plate rotatable on the stock rotating axis, and an array of circularly spaced, spring-loaded centering rollers permitting longitudinal movement through the bearing assembly. A pneumatically operated stock gripper and a bearing assembly enable stock of varying cross-sectional shapes to be pulled to desired positions for cutting. This invention differs from the inventive Tube and Duct Trim Machine in many ways, including its limitation to cutting tube diameters from 0.50 inch to 3.50 inch, it can only cut tube material to length, with end cuts being perpendicular to the longitudinal axis, it does not include a machine vision system to determine the location and angle of a scribe line, and it cannot position and hold nearly any curved configuration of duct details and sub-assemblies.
As can be seen, there is a need for an improved apparatus and method for cutting curved tube and duct assemblies using a high powered laser in conjunction with a vision system, and which can cut a duct or tube of nearly any straight or curved configuration and diameter to a planar scribe line with a high degree of accuracy without the use of dedicated fixturing.
According to one aspect of the present invention, a tube and duct trim machine, is disclosed comprising: a safety enclosure and tooling structure; a traveling overhead gantry and overhead gantry arm movably supported by said trolley; a vertical articulated arm; a plurality of grippers for rigid securement of tubes and ducts to said overhead gantry arm and to said vertical articulated arm; a rotatable and alignable turntable; a tube and duct centering/spatter device; a rough tube and duct positioning alignment unit; a laser cutting system, comprised of a controllable laser cutting head, a fiber optic beam cable and a laser power unit; a vision alignment system, comprised of a plurality of image acquisition modules, and a vision processor module; a machine operator control panel; a main cell controller; a platform mounted controller; whereby said tube and duct trim machine accurately positions and precisely cuts tubes and ducts at a pre-established offset distance from a planar scribe line.
In another aspect of the invention, a tube and duct trim machine, is disclosed comprising: a safety enclosure and tooling structure; an overhead gantry arm and a vertical articulated arm; a plurality of tube and duct grippers; a rotatable and alignable turntable; a tube and duct centering/spatter device; a rough tube and duct positioning alignment unit; a laser cutting system; a vision alignment system; a machine operator control panel; a main cell controller; a platform mounted controller; whereby said tube and duct trim machine accurately positions and precisely cuts tubes and ducts at a pre-established planar scribe line.
In yet another aspect of the invention, a machine is disclosed comprising: a safety enclosure and tooling structure; an overhead gantry arm and a vertical articulated arm; a plurality of grippers; a rotatable and alignable turntable; a centering/spatter device; a rough positioning alignment unit; a laser cutting system; a vision alignment system; a machine operator control panel; a main cell controller; a platform mounted controller; whereby said machine accurately positions and precisely cuts tubes, ducts and other such elements in relation to or relative to a pre-established planar scribe line.
In yet one final aspect of the invention, there is disclosed a method for trimming tubes and ducts, comprising the steps of: selecting and installing appropriate grippers and holding systems to support tubes and ducts; installing proper anti-spatter tubes; roughly positioning and aligning ducts and tubes on a turntable; selecting, on an operator control panel, cutting parameters for the tubes and ducts to be cut; initiating, on said operator control panel, the tube and duct trim machine automatic cutting sequence; removing the cut tube or duct from said tube or duct trim machine.